1. Field of the Invention
The invention relates to a motor-driven working spindle for a machine tool comprising a casing with a central longitudinal axis, a shaft which is mounted for rotation in the casing, a receptacle arranged on a front end of the shaft, an electromotive spindle rotary drive which is coupled to the shaft and is arranged in the casing, the spindle rotary drive comprising a first stator and a first rotor, wherein the first stator surrounding the shaft is mounted in the casing and wherein the first rotor is fastened to the shaft.
2. Background Art
In such a motor-driven working spindle for a machine tool known from US 2005/0236169 A1 the casing mounting the shaft and its spindle-rotary-drive is arranged displaceably on guiding columns. The advancing drive of the entire casing is performed by means of a drive, which is connected in a stationary manner with the columns supporting and guiding the casing. The spindle is advanced by moving the entire casing in which the spindle is mounted axially and displaceably. The advancing movement of the casing is generated by the motor by means of a spindle nut drive. On the end face of the shaft is a tool receptacle, in which a processing tool can be mounted by means of a tool clamping device. For the automatic operation of the tool clamping device in the front part of the shaft clamping jaws are arranged which hold a tool. The clamping jaws are operated by means of a pull rod, whereby the tool is clamped by means of several disc springs, which are effective between the shaft and the pull rod. To release the clamping device the pull rod is displaced hydraulically against the force of the springs. The working spindle can be displaced a relatively large distance in the direction of its axis.
Working spindles known from DE 196 29 991 A1 comprise a shaft that is mounted rotatably in a casing. On the end face of the shaft there is generally a tool receptacle, in which by means of a tool-clamping device a processing tool can be mounted. The tool clamping device can be operated manually; however as a rule it is operated automatically. With these kinds of automatic tool clamping devices in the front part of the shaft clamping jaws are arranged for mounting a tool. The clamping jaws are operated by means of a pull rod, whereby the tool is clamped by means of one or more springs, which are effective between the shaft and the pull rod. To release the clamping device the pull rod is displaced hydraulically against the force of the spring.
Depending on the function of the machine tool the working spindle can reach every predetermined position in the working area of a machine tool. For this it is usual for the working spindle to be installed in a spindle slide, which can be moved in three coordinate directions, including parallel to the central longitudinal axis of the shaft. The working spindle together with the slide supporting it is relatively heavy.
It is also known to design the working spindle to be displaceable in only two axial directions, namely in a plane perpendicular to the central longitudinal axis of the shaft. The displacement in the direction of the central longitudinal axis is performed by displacing the workpiece to be processed in this direction. The workpiece is clamped in this case on a workpiece slide which is displaceable in the direction of the central longitudinal axis of the shaft. The disadvantage of this is that the workpiece slide together with the workpiece forms an extraordinarily heavy system, which has to be adjusted for each processing stage, thereby taking up time and energy.